package com.hjr.leetcode.util;

public class SimpleAES {
    // AES常量定义
    private static final int[] RCON = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};
    
    // S-Box (简化版，实际AES使用复杂计算生成)
    private static final int[][] S_BOX = {
        {0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76},
        {0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0},
        {0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15},
        {0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75},
        {0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84},
        {0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf},
        {0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8},
        {0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2},
        {0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73},
        {0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb},
        {0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79},
        {0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08},
        {0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a},
        {0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e},
        {0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf},
        {0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16}
    };
    
    // 逆S-Box
    private static final int[][] INV_S_BOX = {
        {0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb},
        {0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb},
        {0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e},
        {0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25},
        {0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92},
        {0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84},
        {0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06},
        {0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b},
        {0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73},
        {0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e},
        {0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b},
        {0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4},
        {0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f},
        {0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef},
        {0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61},
        {0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d}
    };
    
    // MixColumns常量矩阵
    private static final int[] MIX_COL_MATRIX = {0x02, 0x03, 0x01, 0x01};
    private static final int[] INV_MIX_COL_MATRIX = {0x0e, 0x0b, 0x0d, 0x09};
    
    private int[][] state;
    private int[][] keySchedule;
    
    public SimpleAES(String key) {
        // 初始化密钥调度
        keySchedule = new int[4][44]; // 4行，44列（11轮密钥）
        expandKey(key);
    }
    
    // 密钥扩展
    private void expandKey(String key) {
        // 将密钥转换为字节并放入前4列
        byte[] keyBytes = key.getBytes();
        for (int i = 0; i < 16; i++) {
            keySchedule[i % 4][i / 4] = keyBytes[i] & 0xFF;
        }
        
        // 生成后续轮密钥
        for (int col = 4; col < 44; col++) {
            int[] temp = new int[4];
            for (int row = 0; row < 4; row++) {
                temp[row] = keySchedule[row][col - 1];
            }
            
            if (col % 4 == 0) {
                // RotWord操作
                int tempVal = temp[0];
                temp[0] = temp[1];
                temp[1] = temp[2];
                temp[2] = temp[3];
                temp[3] = tempVal;
                
                // SubWord操作
                for (int i = 0; i < 4; i++) {
                    temp[i] = S_BOX[(temp[i] >> 4) & 0x0F][temp[i] & 0x0F];
                }
                
                // 与Rcon异或
                temp[0] ^= RCON[(col / 4) - 1];
            }
            
            // 与前4列对应位置异或
            for (int row = 0; row < 4; row++) {
                keySchedule[row][col] = keySchedule[row][col - 4] ^ temp[row];
            }
        }
    }
    
    // 加密函数
    public String encrypt(String plaintext) {
        // 初始化状态矩阵
        state = new int[4][4];
        byte[] plainBytes = plaintext.getBytes();
        
        // 填充到16字节
        byte[] padded = new byte[16];
        System.arraycopy(plainBytes, 0, padded, 0, Math.min(plainBytes.length, 16));
        
        // 将明文放入状态矩阵（按列优先）
        for (int i = 0; i < 16; i++) {
            state[i % 4][i / 4] = padded[i] & 0xFF;
        }
        
        // 初始轮密钥加
        addRoundKey(0);
        
        // 9轮标准操作
        for (int round = 1; round <= 9; round++) {
            subBytes();
            shiftRows();
            mixColumns();
            addRoundKey(round);
        }
        
        // 最后一轮（不进行MixColumns）
        subBytes();
        shiftRows();
        addRoundKey(10);
        
        // 将状态矩阵转换为字符串
        StringBuilder result = new StringBuilder();
        for (int col = 0; col < 4; col++) {
            for (int row = 0; row < 4; row++) {
                result.append((char) state[row][col]);
            }
        }
        
        return result.toString();
    }
    
    // 解密函数
    public String decrypt(String ciphertext) {
        // 初始化状态矩阵
        state = new int[4][4];
        byte[] cipherBytes = ciphertext.getBytes();
        
        // 将密文放入状态矩阵
        for (int i = 0; i < 16; i++) {
            state[i % 4][i / 4] = cipherBytes[i] & 0xFF;
        }
        
        // 初始轮密钥加
        addRoundKey(10);
        
        // 9轮逆操作
        for (int round = 9; round >= 1; round--) {
            invShiftRows();
            invSubBytes();
            addRoundKey(round);
            invMixColumns();
        }
        
        // 最后一轮
        invShiftRows();
        invSubBytes();
        addRoundKey(0);
        
        // 将状态矩阵转换为字符串
        StringBuilder result = new StringBuilder();
        for (int col = 0; col < 4; col++) {
            for (int row = 0; row < 4; row++) {
                result.append((char) state[row][col]);
            }
        }
        
        return result.toString().trim(); // 去除填充字符
    }
    
    // 字节替换
    private void subBytes() {
        for (int row = 0; row < 4; row++) {
            for (int col = 0; col < 4; col++) {
                int value = state[row][col];
                state[row][col] = S_BOX[(value >> 4) & 0x0F][value & 0x0F];
            }
        }
    }
    
    // 逆行移位
    private void invSubBytes() {
        for (int row = 0; row < 4; row++) {
            for (int col = 0; col < 4; col++) {
                int value = state[row][col];
                state[row][col] = INV_S_BOX[(value >> 4) & 0x0F][value & 0x0F];
            }
        }
    }
    
    // 行移位
    private void shiftRows() {
        // 第一行不移位
        // 第二行左移1位
        int temp = state[1][0];
        state[1][0] = state[1][1];
        state[1][1] = state[1][2];
        state[1][2] = state[1][3];
        state[1][3] = temp;
        
        // 第三行左移2位
        temp = state[2][0];
        state[2][0] = state[2][2];
        state[2][2] = temp;
        temp = state[2][1];
        state[2][1] = state[2][3];
        state[2][3] = temp;
        
        // 第四行左移3位（相当于右移1位）
        temp = state[3][3];
        state[3][3] = state[3][2];
        state[3][2] = state[3][1];
        state[3][1] = state[3][0];
        state[3][0] = temp;
    }
    
    // 逆行移位
    private void invShiftRows() {
        // 第一行不移位
        // 第二行右移1位
        int temp = state[1][3];
        state[1][3] = state[1][2];
        state[1][2] = state[1][1];
        state[1][1] = state[1][0];
        state[1][0] = temp;
        
        // 第三行右移2位
        temp = state[2][0];
        state[2][0] = state[2][2];
        state[2][2] = temp;
        temp = state[2][1];
        state[2][1] = state[2][3];
        state[2][3] = temp;
        
        // 第四行右移3位（相当于左移1位）
        temp = state[3][0];
        state[3][0] = state[3][1];
        state[3][1] = state[3][2];
        state[3][2] = state[3][3];
        state[3][3] = temp;
    }
    
    // 列混淆
    private void mixColumns() {
        for (int col = 0; col < 4; col++) {
            int[] temp = new int[4];
            for (int row = 0; row < 4; row++) {
                temp[row] = state[row][col];
            }
            
            for (int row = 0; row < 4; row++) {
                state[row][col] = gfMultiply(MIX_COL_MATRIX[0], temp[0]) ^
                                 gfMultiply(MIX_COL_MATRIX[1], temp[1]) ^
                                 gfMultiply(MIX_COL_MATRIX[2], temp[2]) ^
                                 gfMultiply(MIX_COL_MATRIX[3], temp[3]);
                // 循环移位矩阵行
                int tempVal = MIX_COL_MATRIX[0];
                MIX_COL_MATRIX[0] = MIX_COL_MATRIX[1];
                MIX_COL_MATRIX[1] = MIX_COL_MATRIX[2];
                MIX_COL_MATRIX[2] = MIX_COL_MATRIX[3];
                MIX_COL_MATRIX[3] = tempVal;
            }
            // 恢复矩阵
            MIX_COL_MATRIX[0] = 0x02;
            MIX_COL_MATRIX[1] = 0x03;
            MIX_COL_MATRIX[2] = 0x01;
            MIX_COL_MATRIX[3] = 0x01;
        }
    }
    
    // 逆列混淆
    private void invMixColumns() {
        for (int col = 0; col < 4; col++) {
            int[] temp = new int[4];
            for (int row = 0; row < 4; row++) {
                temp[row] = state[row][col];
            }
            
            for (int row = 0; row < 4; row++) {
                state[row][col] = gfMultiply(INV_MIX_COL_MATRIX[0], temp[0]) ^
                                 gfMultiply(INV_MIX_COL_MATRIX[1], temp[1]) ^
                                 gfMultiply(INV_MIX_COL_MATRIX[2], temp[2]) ^
                                 gfMultiply(INV_MIX_COL_MATRIX[3], temp[3]);
                // 循环移位矩阵行
                int tempVal = INV_MIX_COL_MATRIX[0];
                INV_MIX_COL_MATRIX[0] = INV_MIX_COL_MATRIX[1];
                INV_MIX_COL_MATRIX[1] = INV_MIX_COL_MATRIX[2];
                INV_MIX_COL_MATRIX[2] = INV_MIX_COL_MATRIX[3];
                INV_MIX_COL_MATRIX[3] = tempVal;
            }
            // 恢复矩阵
            INV_MIX_COL_MATRIX[0] = 0x0e;
            INV_MIX_COL_MATRIX[1] = 0x0b;
            INV_MIX_COL_MATRIX[2] = 0x0d;
            INV_MIX_COL_MATRIX[3] = 0x09;
        }
    }
    
    // 伽罗瓦域乘法
    private int gfMultiply(int a, int b) {
        int result = 0;
        int temp = a;
        
        for (int i = 0; i < 8; i++) {
            if ((b & 1) == 1) {
                result ^= temp;
            }
            boolean hiBitSet = (temp & 0x80) != 0;
            temp <<= 1;
            if (hiBitSet) {
                temp ^= 0x1b; // 不可约多项式 x^8 + x^4 + x^3 + x + 1
            }
            temp &= 0xFF;
            b >>= 1;
        }
        
        return result;
    }
    
    // 轮密钥加
    private void addRoundKey(int round) {
        for (int row = 0; row < 4; row++) {
            for (int col = 0; col < 4; col++) {
                state[row][col] ^= keySchedule[row][round * 4 + col];
            }
        }
    }
}
